1. Field
The following description relates to a method and apparatus for compensating for an astigmatism generated due to a beam splitter and an optical pickup device employing the method.
2. Description of Related Art
In an optical pickup device, a path of a light beam from a light source and a path of a light beam reflected from a disc partially overlap with each other in some section. The paths typically overlap with each other within a space between a disc and a beam splitter, and the beam splitter splits the paths into the beam from the light source and the beam from the disc. In particular, the beam splitter causes the beam from the light source to proceed toward the disc, and the beam reflected from the disc to proceed toward a photodetector.
The beam splitter is typically a plate-shaped member that reflects a source beam emitted from a light source to a disc, and transmits a modulated beam or a modulated and reflected beam that is modulated by a recording surface of the disc. While the beam reflected from the disc is transmitted through the beam splitter, the reflected beam is refracted by a first surface facing the disc and a second surface opposite to the first surface. Here, an astigmatism may be generated due to the refraction. Conventionally, however, a sensing lens having a concave shape is used to adjust a spot size of the modulated beam with respect to the light receiving device, without consideration of the astigmatism generated by the beam splitter.